There are numerous instances when a performance of a turbocharger may require qualification. For example, newly manufactured turbocharger units may require a performance test at the manufacturer' facility, or another facility, for a determination of whether there are any performance defects, or whether the turbochargers conform to their functional specifications. In other instances, turbochargers that have undergone a remanufacturing or reconditioning process may also require testing to qualify their performance. In yet other instances, turbocharger performance may require qualification in a service or testing environment as part of an engine troubleshooting process. In any of these instances, various performance parameters of a sample turbocharger unit may be acquired through testing and analyzed.
Techniques previously used for turbocharger performance qualification have included acquisition of various data points within an operational range of a turbocharger for the compilation of a turbine or compressor map, i.e., two dimensional plots of curves representing turbine or compressor performance plotted against a mass flow through the turbine or compressor versus a pressure ratio across the turbine or compressor. Typically, a map is a collection of 20-70 individual running data points that are connected to form curves of constant shaft speed and surge. With interpolation, islands of efficiency are plotted over the curves. These turbine or compressor maps are typically overlaid over what is considered a typical map, to yield a determination of adequacy of a device's performance through visual observation and estimation of the overlay. Interpretation of the results is subjective and does not provide reasonable data to check individual turbo performance.
Such techniques are not practical to implement in a production environment, and even if spot checking is made on sample pieces of a production line, the performance qualification of a turbocharger or one of its components is incomplete and may also be inaccurate as it is based on a visual determination. Moreover, these known techniques are data intensive in compiling the performance maps, time intensive, and costly to implement.
Accordingly, there is a need for an improved method of qualifying performance for turbochargers, that is accurate, does not depend on a subjective determination, and that does not require vast amounts of data to be collected.